During machine welding of large objects a so-called welding crane is often used in order to reach the welding points on the objects. Generally, powder welding is used for welding on large objects, but also other welding techniques may be used. The industry of today requires the possibility to weld increasingly large objects at the same time as the crane on which the weld is arranged shall require as little space as possible. Furthermore, it is desirable that the welding crane has a relatively large range.
The US patent U.S. Pat. No. 3,031,566 A1 describes a welding manipulator with a foldable boom which is movable back and forth and is directed to solve the problem that a fixed welding boom requires a lot of space during use. A telescopic boom is provided in order to solve the problem.
The German utility model DE 761 2106 U describes a welding boom with a supporting pillar which is turnably arranged on a carriage and on which supporting pillar there is arranged a telescopic welding boom.
A problem with telescopic welding booms according to the prior art is that the guides for the telescopic movements requires large space. This means that the innermost boom part must be manufactured with an unnecessarily large cross section from a strength point of view. Such a large cross section means that the access during welding of for example pipes is deteriorated. This problem becomes especially large if the welding crane has three or more segments.